JavaScript is disabled for your browser. Some features of this site may not work without it.

Evaluation of different process designs for biobutanol production from sugarcane molasses

Van der Merwe, Abraham Blignault (2010-03)

Thesis (MScEng (Process Engineering))--Stellenbosch University, 2010.

Thesis

ENGLISH ABSTRACT: Recently, improved technologies have been developed for the biobutanol fermentation
process: higher butanol concentrations and productivities are achieved during
fermentation, and separation and purification techniques are less energy intensive. This
may result in an economically viable process when compared to the petrochemical
pathway for butanol production. The objective of this study is to develop process models
to compare different possible process designs for biobutanol production from sugarcane
molasses. Some of the best improved strains, which include Clostridium acetobutylicum
PCSIR-10 and Clostridium beijerinckii BA101, produce total solvent concentrations of up to
24 g/L. Among the novel technologies for fermentation and downstream processing, fedbatch
fermentation with in situ product recovery by gas-stripping, followed by either
liquid-liquid extraction or adsorption, appears to be the most promising techniques for
current industrial application. Incorporating these technologies into a biorefinery
concept will contribute toward the development of an economically viable process. In
this study three process routes are developed. The first two process routes incorporate
well established industrial technologies: Process Route 1 consist of batch fermentation
and steam stripping distillation, while in Process Route 2, some of the distillation columns
is replaced with a liquid-liquid extraction column. The third process route incorporates
fed-batch fermentation and gas-stripping, an unproven technology on industrial scale.
Process modelling in ASPEN PLUS® and economic analyses in ASPEN Icarus® are performed
to determine the economic feasibility of these biobutanol production process designs.
Process Route 3 proved to be the only profitable design in current economic conditions.
For the latter process, the first order estimate of the total project capital cost is
$187 345 000.00 (IRR: 35.96%). Improved fermentation strains currently available are not
sufficient to attain a profitable process design without implementation of advanced
processing techniques. Gas stripping is shown to be the single most effective process
step (of those evaluated in this study) which can be employed on an industrial scale to
improve process economics of biobutanol production.